Gas density evolution after single nanosecond pulsed discharge: experimental and computational results*

The application of a nanosecond-pulsed discharge across a pin-to-pin air gap was investigated to determine the gas density evolution after a single pulse. Using Rayleigh scattering of a 532 nm pulsed laser, the gas density was compared to the ambient density beginning at 0.3 ms after pulse initiation and continuing to 820 ms after pulse initiation. The scattered Rayleigh signal was measured through a spectrometer with an intensified charge coupled device (ICCD) camera. The results show that after the discharge, the gas density initially decreases between the electrodes. As new air rushes in toward the center of the discharge region, the density begins to increase to ambient conditions between the electrodes, while the lower density air that surrounds the region is pushed outwards. Five hundred microseconds after the nanosecond-pulsed discharge was initiated, the gas in the 4-mm region surrounding the electrodes returns to pre-discharge conditions. The experimental results are compared with computational models from Ansys/Fluent to elucidate the fluid mechanical phenomena associated with the discharge.